This invention relates to a self-expanding stent catheter with a low pressure, anchor and/or marker balloon assembly within the field of peripheral angioplasty. More specifically, this invention relates to accurate stent placement of a self-expanding stent for deployment at a stenotic segment site within a patient's vascular system while concomitantly maintaining lumen blood flow during an angioplasty stenting procedure.
The vascular bed in humans is a complex and an extensive network of lumens carrying blood and delivering oxygen and nutrients throughout the skeletal network, organs and muscle tissues of the body. At a macro level the human circulatory system can be logically characterized as originating from the heart with an initially ascending aorta arch extending from the left ventricle upwardly and then descending generally vertically downward via a central lumen column through a patient's thoracic region and diaphragm to an abdominal aorta segment. The aorta terminates into common left and right iliac arteries extending down into lower extremities. In broad brush terms a sequence of blood flow is from a left heart ventricle to the aorta, to arteries, to arterioles, to venules, to veins, and to a vena cava back to a right side of the heart.
The aorta provides a base for systemic circulation of blood for the entire body. Right and left coronary branches extend from an aortic root to supply a patient's heart while the aortic arch supplies blood to the patient's head, neck and arms. Branches from the thoracic aorta supply the chest and branches from the abdominal aorta supply the abdomen while the pelvis and lower extremities are fed from common iliac arteries extending from a base region of the aorta.
Vascular lumens are composed of elastic tissue which can, over time, become somewhat hardened in a disease zone due to an internal accumulation of cholesterol laden plaque, which is a fatty material composed of cholesterol and other particles which build up within an artery wall to create a narrowing (stenosis) of the artery. Plaque stenotic segments can decrease vessel elasticity and concomitantly impair blood flow and in acute instances even occlude a free flow of blood through the lumen. This malady is sometimes referred to as atherosclerotic arterial disease.
In 1964 an vascular radiologist by the name of Charles Dotter, often referred to as the “Father of Interventional Radiology” pioneered development of angioplasty and a catheter delivered stent as a treatment for peripheral arterial disease.
Stents are now universally used in percutaneous coronary and peripheral angioplasty procedures, which effectively open narrowed blood vessels. A stent is a tiny, expandable, cylindrical wire mesh scaffolding. A stent may be formed as a cylindrical, self-expanding unit which is delivered to a stenotic site in a collapsed posture within a covering retention sheath or collar. Once the stent is in position the sheath or collar is axially withdrawn and the self-expanding stent radially extends and compresses a stenotic site within a patient's diseased lumen.
An interventional physician uses radiography, an X-ray procedure, to identify a stenosis location and estimates the size of a diseased blood vessel and severity of stenotic plaque narrowing. Blood vessels are not visible by X-ray, per se, however, by injecting a contrast media (dye) through a catheter sheath a trained physician is capable of accurately viewing arterial boundaries with the pulsating flow of blood through downstream arteries and develop an accurate sense of a stenotic site requiring interventional correction.
Placing a stent at a site of a stenosis in a downstream segment of a blood vessel is a routine process performed by an interventional physician; however, placing a stent when the stenosis is at a bifurcation, is complex. Positioning a stent too distal may miss part of a narrowing stenosis while positioning a stent too proximal may result in proximal end of the stent protruding into a primary blood vessel.
Accurately and effectively addressing a plaque stenosis at certain sites within a human circulatory system can be challenging. One region of special interest is peripheral angioplasty with stenting to osteal and proximal segments of the iliac arteries.
It is not uncommon, to encounter stenotic disease at the abdominal aortic bifurcation which might involve both iliac arteries. Angioplasty in this instance may require advancing self-expanding stents, from both common femoral arteries, one from each side, into the lower abdominal aorta, with simultaneous expansion of both self-expanding stents (kissing stents), creating two channels in the abdominal aorta, one into each iliac artery.
The result in such bilateral procedures are usually effective and the obstruction resolves. Allowing distal stent struts in the abdominal aorta, however, may hinder future peripheral intervention when a physician elects a cross over approach. In the cross over approach, angioplasty is carried out using the common femoral access to fix a blockage in the contralateral lower extremity. In this case a stiff guide wire is introduced from the right or the left common femoral arteries, into the abdominal aorta and down to the contralateral iliac and femoral vessels. A long vascular sheath is introduced over the wire, across the abdominal aortic bifurcation, into the contralateral side. The peripheral angioplasty is therefore carried out using the right access to the left lower extremity and vice versa.
Having the stent struts, in the abdominal aorta from a previous angioplasty to the iliac vessels, would eliminate the future option of contralateral approach, forcing an interventional physician to access the lower extremity through an upper extremities, a more complex risky and prolonged approach which may not be possible. Alternatively a patient may be subjected to an operative procedure for lower extremities vascular surgery.
Proper positioning of the stents at the opening of the iliac arteries, using an anchor and marker fluid in the anchor balloon or balloons at the distal end of the stent, will minimize stent strut protrusion into the abdominal aorta and thus will keep the option of future crossover peripheral angioplasty approach available.
The limitations suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness, reliability and physician satisfaction with prior methods and apparatus for angioplasty, with stenting, at stenotic sites within a patient's vascular system. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that present angioplasty methods and apparatus, involving stenting a stenotic lumen in a patient's circulatory system, appearing in the past, will admit to worthwhile improvement.